1. Field of the Invention
The present invention relates generally to an apparatus and method of controlling a linear compressor, and more particularly to an apparatus and method of controlling a linear compressor, which is capable of preventing collisions between the piston and valve of the linear compressor, thereby improving the operational efficiency of the linear compressor.
2. Description of the Prior Art
As depicted in FIG. 1, a linear compressor 1 is comprised of a drive unit 2, a resonance spring 3, a displacement restricting unit 4, a valve 5, a cylinder head 6, a piston 7 and a cylinder block 8.
A conventional apparatus to control the operation of a linear compressor is described below.
Referring to FIG. 2, the conventional control apparatus is comprised of a core 10, first and second coils 12 and 13, a signal processing unit 20 and a microcomputer 30. The core 10 is made of a magnetic substance and moved in conjunction with a part (that is, a piston) whose position is desired to be detected, the first and second coils 12 and 13 are symmetrically wound around the core 10, and the signal processing unit 20 detects and outputs variations in position of the core 10 using voltages induced to the first and second coils 12 and 13.
The signal processing unit 20 is comprised of a first full-wave rectification unit 21, a second full-wave rectification unit 22, a differential amplification unit 23, a filter unit 24, and a peak detection unit 25. The first full-wave rectification unit 21 full-wave rectifies the voltage induced to the first coil 12, the second full-wave rectification unit 22 full-wave rectifies the voltage induced to the second coil 13, the differential amplification unit 23 amplifies a difference between the voltages full-wave rectified by the first and second full-wave rectification units 21 and 22, the filter unit 24 eliminates a high-frequency component from a signal outputted from the differential amplification unit 23, and the peak detection unit 25 detects the maximum and minimum values of a signal outputted from the filter unit 24, and transmits the detected values to a microcomputer 30.
The operation of the conventional linear compressor is described below.
If the position of the core 10 is varied by a variation in position of a part (for example, the piston) whose position is desired to be detected while alternating current (AC), having a frequency of several KHz, is applied to the first and second coils 12 and 13 from the outside, voltages in proportion to the variation in position of the core 10 are induced to the first and second coils 12 and 13. The voltages induced to the first and second coils 12 and 13 are full-wave rectified by the first and second full-wave rectification units 21 and 22, and the full-wave rectified voltages are inputted to input terminals of the differential amplification unit 23. The differential amplification unit 23 amplifies a difference between the voltages full-wave rectified by the first and second full-wave rectification units 21 and 22, and outputs the amplified difference to the filter unit 24. The filter unit 24 eliminates a high-frequency component from the signal outputted from the differential amplification unit 23, and outputs the filtered signal to the peak detection unit 25. The peak detection unit 25 full-wave rectifies the signal outputted from the filter unit 24, and outputs the rectified signal to the microcomputer 30. The microcomputer 30 controls the stroke of the linear compressor 1 according to the signal rectified by and outputted from the filter unit.
The conventional linear compressor control apparatus controls only a stroke detected by a sensor, etc., so the stroke of the linear compressor can be controlled to be constant. However, in the linear compressor the center position of whose piston is varied according to load, a top clearance cannot be kept constant with respect to the top dead center of the piston. As a result, there occurs a problem that the piston of the linear compressor is brought into collision with the valve of the linear compressor.
Accordingly, it is an object of the present invention to provide an apparatus and method of controlling a linear compressor, which is capable of controlling a top clearance for the top dead center of the piston of the linear compressor, thus preventing the collision between the piston and valve of the linear compressor and improving the operational efficiency of the linear compressor.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing an apparatus to control a linear compressor, comprising: a current detection unit to detect current supplied to the linear compressor; a control unit to determine whether a collision between a piston and a valve of the linear compressor occurs by using an output signal from the current detection unit, and controlling a stroke of the linear compressor if the collision occurs; and a compressor drive unit to perform adjustment of the stroke of the linear compressor in response to control of the control unit.
In addition, the present invention provides a method of controlling a linear compressor, comprising: presetting a maximum stroke and a collision point according to a load; selectively increasing and reducing a stroke of the linear compressor according to a variation in the load; and controlling the stroke according to a variation in current supplied to the linear compressor.